This invention relates generally to an electrostatographic printing or copying machine which utilizes multiple toners, such as in the formation of multi-color images and more particularly, cleaning brushes to remove toner additive film particle buildup on the photoconductive member.
In a colored image forming apparatus, an electrostatic latent image which is to be developed by a predetermined color is formed on a photoconductor by an optical system of a copying machine or printer. Then, the electrostatic latent image is developed by a developing unit which accommodates a predetermined colored toner to be used for development. This toner image may be subsequently transferred to a support surface such as copy paper or other medium to which it may be permanently affixed by heating or by the application of pressure. After each transfer process, the toner and other debris particles (i.e. residual particles) remaining on the photoconductor is cleaned by a cleaning device.
The brush bias latitude of an electrostatic brush (ESB) cleaner is defined by evaluating performance at a number of brush bias conditions. A setpoint is chosen by stressing the input to the cleaner and choosing the point upon which the latitude converges. This is fairly straightforward process when single toner type systems are used. However, when multiple toner types are used a problem is encountered. The latitudes may, in fact, converge to different brush bias setpoints. This has been observed, for example, in cleaning latitude tests conducted on a Xerox 5090 with one additional color station added. With the Xerox 5090, the black toner bias setpoint convergence was different than for the red toner.
The following disclosure may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,533,236 to Garsin discloses a magnetic brush cleaner for removing residual charged particles such as toner from a charge-retentive surface such as a photoreceptor. The brush cleaner has a bias voltage applied thereto for establishing an electrostatic field for aiding in toner removal. A control is provided for varying the bias voltage applied to the brush cleaner in accordance with variations in photoreceptor potential to thereby maintain the cleaning potential (i.e. the difference between the applied bias voltage and the photoreceptor potential) invariant.